We have a SEO Audit service, and we are always in the look for new issues to detect. So far we have about 50, and most webmasters should be aware of those. On average, a website incurs in 30-35 faults that negatively influence its rankings.
The issues are divided into insite and offsite. The insite are the easiest to fix, and the offsite factors, mostly link related, are to be addressed with method and patience.
We are offering an installment plan, that also offers a monthly update on the standing issues. The idea is that sites are to be permanently monitored for negative ranking factors.
We collected a number of software resources to make checking faster. Some are links, some are software packages, some are scripts that run in our pages. This arsenal allows us to run deep analysis in a day or two. This is not intended to discourage imitators: most tools are publicly known. But of course it requires a lot of time of dedicated programmers, which we offer to our clients.
Check the above cited page and if you are really interested, ask for a sample of our work, or for the complete model report that we send to our clients.
Our interest is mainly to earn money providing service, but also to correlate the SEO Audit issues with ranking: as a result, we improve our knowledge of what is important for ranking.